This invention relates to plasma displays and a method of operation for improved efficiency. More particularly, this invention relates to a full color, high resolution capable AC Plasma Display, commonly known as a PDP monitor, having a front or top viewing plate and micro-grooves on a back-plate enclosing gaseous discharges which emitt UV light and excite light emitting phosphors on the micro-groove surfaces. Such displays have application for computer screens and TV, but typically operate at low efficiency compared to CRT tubes.
A flat-panel display is an electronic display in which a large orthogonal array of display devices, such as electro-luminescent devices, AC plasma display panels, DC plasma panels and field emission displays and the like form a flat screen.
The basic structure of an AC Plasma Display Panel, or PDP, comprises two glass plates with a conductor pattern of electrodes on the inner surfaces of each plate and separated by a gas filled gap. The conductors are configured in an x-y matrix with horizontal electrodes and vertical column transparent electrodes deposited at right angles to each other using thin-film techniques well known in the art. The electrodes of the AC-plasma panel display are covered with a thin glass dielectric layer. The glass plates are assembled together to form a sandwich with the distance between the two plates fixed by spacers. The edges of the plates are sealed and the cavity between the plates is evacuated and back-filled with neon and argon or a similar gas mixture. When the gas ionizes, the dielectrics charge like small capacitors so the sum of the drive voltage and the capacitive voltage is large enough to excite the gas contained between the glass plates and produce a glow discharge. As voltage is applied across the row and column electrodes, small light emitting pixels form a visual picture.
Barrier ribs are typically disposed between the foregoing insulating substrates so as to prevent cross-color and cross-pixel interference between the electrodes and increased resolution to provide a sharply defined picture. The barrier ribs provide a uniform discharge space between the glass plates by utilizing the barrier ribs height, width and pattern gap to achieve a desired pixel pitch. For example, barrier ribs of plasma display panels most desirably have a configuration of about 100 xcexcm in height and are as narrow as possible, preferably less than 20 xcexcm in width and spaced at about 120 xcexcm pitch. This requirement is necessary in order to achieve a color pixel pitch of 72 lines per inch, the printing industry standard point of type, which is equivalent to a sub-pixel pitch of 216 lines per inch with a red, green and blue phosphor stripe color arrangement. This pattern is commonly used to achieve color output in flat panel and many cathode ray tube displays with diagonal dimensions on the order of 20 to 40 inches used for displaying graphic and textual information in computer terminal equipment and television receivers.
An alternative geometry for an AC PDP is given according to U.S. patent application Ser. No. 08/629,723, incorporated herein by reference. In a PDP of this type, the backplate is manufactured by first constructing an array of microgrooves, metalizing the recessed surfaces of the microgrooves, applying a phosphorescent material on the microgroove surfaces co-incident with the metalized surfaces, and sealing with a front plate containing a dielectrically isolated conductor array generally orthogonal to the microgroove array, i.e., metal on groove (MOG) structure.
Flat panel displays, such as AC plasma display panels (AC-PDPs) are desired to have large screens, large capacity, and the ability to display full-color images. In particular, the AC PDPs must provide more display lines and intensity levels and reliably rewrite their screens without decreasing the luminance of the screens, but all at reasonable power.
It is an object of the invention to provide an improved panel structure and method and apparatus for driving an AC plasma display panel with high efficiency. Another object of the present invention is to provide a method and an apparatus for driving a lateral discharge plasma display panel that is capable of displaying 256 shades of gray at lower voltages than possible with the prior art.
Briefly, according to this invention there is provided a method of operating an AC plasma flat-panel display having a hermetically sealed gas filled enclosure. The enclosure includes a top transparent substrate and a bottom substrate spaced from but in contact with top substrate. The top substrate has an array of paired top electrodes and an electron emissive and insulating film covering the top electrodes but with a newly invented microchannel under and parallel to said top electrodes. The bottom substrate has a plurality of parallel micro-grooves arranged orthogonally to the top electrodes and a bottom electrode formed of metal and deposited within each microgroove having a bottom and side-walls and a phosphor material deposited on and coincident with each bottom electrode thereby forming sub-cell pairs called sub-pixels at the projected intersections of the top electrodes forming rows and microgrooves forming columns. However, the bottom substrate may be of several prior art types but advantageously of the MOG geometry as just described.
In general the method comprises the steps of:
applying a sustain step comprised of applying a first voltage to first electrodes of top electrode pairs and a second voltage, of opposite polarity to the first voltage, to the second electrodes paired with the first electrodes which creates discharges between sub-cell pairs which have charges stored on the dielectric under corresponding top electrodes,
maintaining the voltages until discharges extinguish thereby depositing charges under the top electrodes of opposite polarity
applying first terminating voltages to first top electrodes and second terminating voltages to second top electrodes as necessary to sweep residual charges in gas volume, and
reversing the polarities of first and second top electrodes and repeating the sequence continuously in conjunction with optional selective addressing steps which include:
applying a selective write step comprised of applying a write voltage of common polarity to a preceding or co-incident sustaining voltage to a first electrode of one or more pairs of top electrodes and a common write voltage to all bottom electrodes,
applying a second write voltage, of opposite polarity to the first, to the second electrode paired with the first electrode causing discharges to initiate and spread along the top substrate microchannels, and
maintaining the voltages until discharges extinguish thereby depositing and storing charges on dielectric coating under the top electrodes along the entire row; and
applying a selective erase step comprised of applying an erase voltage of opposite polarity to a preceding sustaining voltage to a first electrode of one pair of top electrodes and a column voltage to selected bottom electrodes, the resulting voltage of combined magnitude sufficient to cause a discharge only at sub-cell sites which have charges stored under corresponding top electrodes, and
maintaining the voltages until discharges extinguish thereby removing stored charges which prevent discharging at subsequent sustain steps.
For a MOG device the method comprises the steps of:
applying a sustain step comprised of a first voltage to first electrodes of top electrode pairs and a reference voltage to all bottom electrodes, the difference of sufficient magnitude to cause an initiating discharge to sidewalls of bottom electrodes intersected at the Paschen minimum only for sub-cells which have charges stored under corresponding top electrodes, and
applying a second voltage, of opposite polarity to the first voltage, to the second electrodes paired with the first electrodes which creates lateral discharges between virtual electrodes, formed by the initiating discharges to sidewalls, between sub-cells pairs at pressure gap product values greater than the Paschen minimum,
maintaining the voltages until discharges extinguish thereby depositing charges under the top electrodes but of opposite polarity,
applying first terminating voltages to first top electrodes and second terminating voltages to second top electrodes as necessary to sweep residual charges in gas volume, and
reversing the polarities of first and second top electrodes and repeating the sequence continuously in conjunction with optional selective addressing steps comprising:
applying a selective write step comprised of applying a write voltage of common polarity to a preceding or co-incident sustaining voltage to a first electrode of one or more pairs of top electrodes and a selective write voltage to selected bottom electrodes, the difference of sufficient magnitude to cause a discharge to sidewalls of all bottom electrodes intersected at the Paschen minimum in conjunction with applying second write voltage, of opposite polarity to the first, to the second electrode paired with the first electrode causing discharges to initiate and spread along the top microchannels, and
maintaining the voltages until discharges extinguish thereby depositing and storing charges on dielectric coating under the top electrodes along the entire row; and
applying a selective erase step comprised of applying an erase voltage of opposite polarity to a preceding sustaining voltage to a first electrode of one pair of top electrodes and a column voltage to selected bottom electrodes, the resulting voltage of combined magnitude sufficient to cause a discharge to sidewalls of the selected bottom electrodes at the Paschen minimum but only at sub-cell sites which have charges stored under corresponding top electrodes, and
maintaining the voltages until discharges extinguish thereby removing stored charges which prevent discharging at subsequent sustain steps.
In any case, the key element is that the tunneling of discharges through the microchannels in the top, or front viewed, substrate can with certain waveforms lower the writing voltage for addressing and the maximum sustain voltage. This, in combination with a higher efficiency gas mixture and an addressing waveform to exploit it, allows a display with higher operating efficiency to be made.